2 on the top with generic no-name bike carriers
2 kidīs bike on a tail mounted Mont Blanc carrier, minus the wheels as they are cantilevered out so far and the kidīs bike weigh a ton.

The surfboard is an 8ī6" stepped pintail minimal.

Both work well, in fact we had 3 on top and 3 on the back coming home from Sweden in July.

I tape down the top of the front fender round the tyre and rim with duct tape to keep it out of the wind.